Recently theoretical frameworks have been introduced for integrating current theories of the neuroscientific and developmental pathways by which family risk translates into ADHD phenotypes. It has been proposed that for some children with ADHD, early deficits in executive functioning (EF) abilities have precipitated the disorder. Early disruptions in delay reward signaling have been proposed as a second developmental neuroendophenotype of ADHD, wherein high approach temperament may lead to ADHD. Evaluating these proposed neuroendophenotypes requires assessment in infancy, when candidate processes first emerge. We will also investigate the relationship of EF and temperament during infancy, testing the high approach temperament will be associated with an impulsive response style that disrupts performance on response inhibition tasks. We propose to investigate differences in emergence of EF ability associated with family risk for ADHD. Infants will be recruited into two groups: Those with (n=50) and those without (n=50) a family history of ADHD. These 10-month-old infants will be assessed with state-of-the-art tasks of response inhibition, working memory, and temperament. We will test the prediction that infants in the family-risk group will have lower EF scores and higher approach temperament than infants in the non-family risk group. The proposed study is positioned to make a unique contribution to developmental taxonomies of ADHD because we will investigate abilities that specify at-risk neurological sub-straits and evaluate their interaction in infancy. Currently, theories of the etiology of ADHD are at best hampered, and, at worse, driven off course by the lack of data about key neuropsychological functions in infancy. Identifying at-risk profiles earlier will inform our understanding of how behavioral and neurological development in this domain go awry and suggest avenues for targeted interventions. This is an opportunity to utilize recent advances in infant neuropsychological to better understand the psychopathology of the most common childhood psychiatric disorders. Identifying at-risk profiles earlier will inform our understanding of how behavioral and neurological development in this domain go awry and suggest avenues for targeted intervention. This is an opportunity to utilize recent advances in infant neuropsychological to better understand the psychopathology of the most common childhood psychiatric disorders. [unreadable] [unreadable] [unreadable]